Revascularization using graft materials having tubular structure has been attempted in order to treat the vascular disorder due to complication of diabetes, cancer, rheumatism or the like. When a graft material is embedded in a damaged site, a cell inherent to a living body or a cell implanted together with the graft material regenerates the tissue using the graft material as a scaffold, and forms a neovascular vessel.
The graft material is formed of a bioabsorbable material, and is decomposed and absorbed in a living body; however, until the tissue is regenerated after the implantation, the graft material remains at the implantation site without being decomposed, and offers a scaffold and a space for the tissue to be regenerated. The formation of a tubular structure from the graft material can secure the scaffold and the space for such a regenerated tissue in the lumen.
As a graft material having a tubular structure, Patent Literature 1 discloses “a tubular medical material for living tissue regeneration, wherein a first yarn made of a multifilament of a bioabsorbable polymer and a second yarn made of a monofilament of a bioabsorbable polymer are combined and disposed alternately or in an appropriate ratio into a cylinder constituted with a braid-like or tubular knit like tissue” (see claim 1). It is stated that this tubular medical material allows the interior of the cylinder to be a cavity, thus does not disturb the flow of the liquid for regeneration of living tissue, and can prevent the leakage of the liquid inside the lumen (see paragraph 0008 in the aforementioned literature). Patent Literature 1 does not describe the adoption of a multitubular structure for the graft material.
In addition, Non Patent Literature 1 states that “the development of many materials such as polylactic acid and polyglycolic acid as fibrous artificial polymer materials has proceeded, and such materials can also be selected according to applications; a plurality of basic yarns (diameter: 10 μm) of a tissue-dissolution type material were woven to prepare a hollow tube, and various adhesion molecules were bound; setting of a knitting machine allows scaffolds having shapes of many different sizes and shapes to be constructed.” (p. 46, left column, lines 6 to 2 from the bottom, in the aforementioned literature). Moreover, it is stated that “the present method has been proved to be a method effective for neural circuit reconstruction in such a limited space as cerebrospinal” (p. 47, left column, lines 15 to 17, in the aforementioned literature); however, it has not been stated that the method can be applied to blood vessels.
Moreover, with respect to a scaffold material for revascularization, Patent Literature 2 discloses a scaffold material which is a hollow cylinder formed of a plurality of concentric layers, and a cylinder formed of aliphatic polyester fiber. The scaffold material is a cylinder formed of a plurality of layers, prepared by winding the fibers obtained by spinning a dope including an aliphatic polyester with an electrospinning method, and is regarded as a material having a structure similar to the structure of blood vessels and a mechanical strength comparable to the mechanical strength of blood vessels (see, p. 2, lines 15 to 22, in the aforementioned literature). In the scaffold material, the plurality of layers are mimetic to the vascular intima, media and adventitia of the actual blood vessel tissue (see, p. 7, lines 1 to 12, ibidem), and the layers are regarded as adhering to each other.